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Which component shows spin squeezing under twisting Hamiltonian?

There is a contentious debate emerging about whether this question, currently at revision 5, should be open or not. Standard practice is to bring the discussion to meta, so here we are to discuss: is it right for revision 5 to be on hold or not, and why?

To clarify: I think there's agreement that the question should be on hold according to the current homework policy. Here we should address whether whatever new policy we come up with should also put such questions on hold.

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I think that this type of question should not be closed. It is not wrong/out-of-present-day-physics, or incoherent or without a reference for context. Even if I might think that this is homework for a graduate level course.

I strongly believe that at graduate level a physicist will stand or fall by the research he/she can do and the purpose of this board should not be to teach diligence/the-honor-system to graduate students. It seems to me that the site aims to be a web repository of knowledge where somebody googling for "twisting Hamiltonian" will find a relevant answer and links to the context.

It will be a pity if it ends up a repository on simple conceptual problems in physics ( these I can easily answer because my mathematical tools are rusty). I have lost count on how many times I have contributed to answer the "wave particle duality" connundrum.

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  • $\begingroup$ Note that it was closed before any reference or context was added. And then when it was added, the information was found in the references. $\endgroup$
    – Kyle Kanos
    Feb 24, 2014 at 13:38
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    $\begingroup$ @KyleKanos If this is so, one could have asked for a clarification of context before closing, no? Also he was a new user, one should be more lenient and give the benefit of the doubt, imo. Anyway, as an experimentalist I found it interesting because I had not heard of a "twisting Hamiltonian"before. $\endgroup$
    – anna v
    Feb 24, 2014 at 13:48
  • $\begingroup$ I don't know how I feel about being lenient on new users... I think newer users who have demonstrated a desire to participate at a deeper level than "I have homework please help me" should be given a little more latitude than brand new users with no track record of interest. But to that point, that's why things were changed from "Closed" to "On Hold" rather than "Get off our site you n00b." It's softer language already, which to me is their leniency. But maybe I'm just a grumpy 28 year old :) $\endgroup$
    – tpg2114
    Feb 25, 2014 at 2:23
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The question seems mostly to be within a quote block, but I can't tell whether it's a quote from somewhere (e.g. a textbook or past exam paper) or whether the user just randomly put quotes around the question for no reason.

edit: the quote block was edited in by someone other than the OP. I've now removed it.

If the former then it obviously should be closed according to the current policy. I don't think there's any room for debate there. The policy says that homework questions should show some effort, which clearly isn't the case here, with the question in its current form.

There is room for debate about whether it should be allowed by any future policy (honestly I'm on the fence about that), but since the new policy isn't in effect yet I'd say it should stay closed, at least until the user can reword it so it doesn't look like a verbatim quote from somewhere.

Of course, if this is just a case of "random quotation marks" then there's no problem except the formatting. In that case it's a conceptual question and the user has made some effort to specify it clearly, and it should be easy enough for the OP to edit so that it doesn't give the impression of being a copy-and-paste.

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    $\begingroup$ It is not a quote from somewhere, but a honest question the OP is asking about this particular physical system described by a twisted Hamiltonian (not heard about this before in that context). The container box was edited in later, so it is a purely formatting issue indeed. Not being allowed to ask technical questions about specific physical systems defeats the whole purpose of learning physics at a deeper level, and if Physics SE indeed disallows these technical questions, all that is left to be allowed are popular non-technical equation free conceptual questions. $\endgroup$
    – Dilaton
    Feb 23, 2014 at 10:14
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    $\begingroup$ As it is a conceptual question too, it really should be reopend and users who think so are free to vote accordingly. $\endgroup$
    – Dilaton
    Feb 23, 2014 at 10:18
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    $\begingroup$ I see now that the quote block was edited in by someone other than the OP. How odd. I've removed it, and (assuming it really isn't quoted from somewhere) I now agree with you that it makes absolutely zero sense to consider this a homework question, either under the current policy or any reasonable future one. $\endgroup$
    – N. Virgo
    Feb 23, 2014 at 10:26
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    $\begingroup$ I mean, in the same way as 5 people (or a mod) can close a question just like that because they think it is the right thing, it should be equaly easy for 5 other people who disagree with this to reopen it without having to go through huge bureaucratic obstructions or meta discussions. This is how community moderation should work, as often said even on MSO. I disagree with the large asymmetry perceived on Physics SE, that it is very easy to close a question but people who want a question to be reopend have always to face and overcome large bureaucratic obstructions. $\endgroup$
    – Dilaton
    Feb 23, 2014 at 10:40
  • $\begingroup$ I added the quite block because it looked like a question straight out of a textbook (especially with the now removed first line). $\endgroup$
    – Kyle Kanos
    Feb 23, 2014 at 11:52
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    $\begingroup$ @KyleKanos you should not have done that just because you personally assumed without any objective proof (!) that it was straight out of a textbook without any proof. Doing such a thing in order to mislead subsequent reviewers and readers of the question, in order to bias them towards agreeing with your strong personal dislike of the question to prevent it from getting reopend, was outright dishonest to say the least, not cool! I am appalled by what measures you are capable of taking in order to enforce your personal opinion ... $\endgroup$
    – Dilaton
    Feb 23, 2014 at 12:30
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    $\begingroup$ @KyleKanos it's written somewhat in the style of a textbook question, but I don't see any overwhelming reason to conclude that it actually is one. $\endgroup$
    – N. Virgo
    Feb 23, 2014 at 15:20
  • $\begingroup$ @Dilaton: In order of your sentences: Guilty (though note that you used "without any proof" redundantly). Not guilty, I did it because it had every outward appearance of being a homework problem. No you're not. New comment: you do realize that I was the one who gave the answer to the OP right? What is it that you've done in the comments? Right, complain that it should be reopened. You've made your point, move on in life please. $\endgroup$
    – Kyle Kanos
    Feb 23, 2014 at 18:02
  • $\begingroup$ @Nathaniel: If it looks like a duck, swims like a duck, and sounds like a duck, it probably is a duck. $\endgroup$
    – Kyle Kanos
    Feb 23, 2014 at 20:02
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    $\begingroup$ @KyleKanos I don't think the evidence is really that strong. It looks a bit like a duck, but could well be a platypus. I think a more appropriate aphorism is ei incumbit probatio qui dicit, non qui negat. $\endgroup$
    – N. Virgo
    Feb 24, 2014 at 0:46
  • $\begingroup$ @Nathaniel: And your disagreement is the whole reason that the SE model works. If enough people agree with a particular close-voter that it looks like a duck, it's a duck. If enough people disagree, it's a platypus. $\endgroup$
    – Kyle Kanos
    Feb 24, 2014 at 1:16
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The question asking about some properties of a twisted Hamiltonian system is conceptual, even though it asks about the issue at a technical level. It not less conceptual than the more basic question brought up here and who's attracting closevotes is questioned too, but the twisted Hamiltonian question is about a more advanced topic and at a higher level.

As already said several times (and please dont ignore the fact that my answer there is the one with the highest net scoere so there are people who agree with this even on meta) elsewhere, technical questions, as they come up from reading books about advanced topics, following higher level courses, or even from studying research papers should not be prohibited. Forbidding such technical questions about advanced topics is detrimental for people who want to learn physics at a beyond popular equation free technial level, and it would be bad for the originally targetted audience of the site (researchers, academics, and students of physics and astronomy).

The twisted Hamiltonian question is a legitimate technical question too, it is even conceptual, so IMHO the closevoters have been wrong. In summary, this particular question should not be closed, but allowed to attract nice and interesting answers.

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    $\begingroup$ And as I said here, asking technical questions about issues one does not understand from reading (research) papers, books, etc is IMHO a legitimate and natural use of a site in order for people to help each other improve their physics knowledge. Selectively preventing technical questions is rather detrimental for people interested in learning physics at an advanced level. $\endgroup$
    – Dilaton
    Feb 23, 2014 at 7:36
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    $\begingroup$ The current practice of stigmating and closing good technical questions about rather advance theoretical topics discourages potentially good contributors from taking part in the site; it is a disservice for the site, and it is among the reasons why I can no longer ask questions on the main site either ... $\endgroup$
    – Dilaton
    Feb 23, 2014 at 7:37
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    $\begingroup$ -1. The question has no concept about it, unless your definition of "concept" is radically different than everyone else's. $\endgroup$
    – Kyle Kanos
    Feb 23, 2014 at 11:50
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    $\begingroup$ Shouldn't we require some effort from the OP? Otherwise, to a one page paper I would be asking hundreds of questions here. $\endgroup$
    – jinawee
    Feb 23, 2014 at 23:27
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It was rightfully closed in the first place. As it was originally written, it had every appearance of a graduate-level but zero effort homework problem. After it was closed, OP added a couple relevant links to papers that contained the answer (as pointed out by me). Seems to me that it's still a zero-effort homework problem.

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    $\begingroup$ The question is, can it be improved to a conceptual one? Most high-level HW questions have a conceptual confusion at their heart. After looking through the comments, do you think you can identify it? Or is it not there? $\endgroup$
    – Manishearth
    Feb 23, 2014 at 2:26
  • $\begingroup$ @Manishearth: Well the first two question are almost axioms for spin squeezing, so definitely no on those two. AFAIK, spin squeezing disappears when $\langle J_z\rangle=0$, so the third question appears to be also a no. $\endgroup$
    – Kyle Kanos
    Feb 23, 2014 at 2:52
  • $\begingroup$ @Manishearth (3 comments up) while we do need to consider that, the purpose of this meta question is not whether the question can be edited to be appropriate, but whether it is appropriate in its current form. $\endgroup$
    – David Z
    Feb 23, 2014 at 3:17
  • $\begingroup$ @DavidZ Sure, but I wanted to run a parallel discussion on that. I agree with Kyle's stance on the original post, but I feel that we as a community should put more effort into getting these (grad level HW) posts fixed. $\endgroup$
    – Manishearth
    Feb 23, 2014 at 3:25
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    $\begingroup$ @Manishearth I can maybe be convinced that undergrads and high schoolers are only placed on Earth to know facts, not be intelligent, and so we should spoon feed them. But grad students?? If they can't articulate themselves or do even a modicum of research at their level then what is society paying them for? $\endgroup$
    – user10851
    Feb 23, 2014 at 4:09
  • $\begingroup$ @ChrisWhite there is no need for being zynical and scornful here. Sometimes I really wish I could downvote comments ... $\endgroup$
    – Dilaton
    Feb 23, 2014 at 7:14
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The way the question is worded seems to me to be indicative of being copied and pasted out of a textbook or a problem set. In particular, the phrase

Can you answer this without assumptions on the initial state?

is characteristic of how one would write a homework problem, but not how one would ask an honest conceptual question. Therefore I think it should be on hold.

The OP has clarified that this is not copied from somewhere, in this case, although I think the more general point about the phrasing stands.

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    $\begingroup$ This is simply not the only reasonable but the least sympathetic and most obvious (personal) interpretation for people who want to close the question by all means. Can you answer this without assumptions on the initial stat can as well mean that the the OP wants to know if these the proparties of the system he askes about are independent from the initial state, which is as everybody who knows some statistical mechanics sees, a completely legitimate and even conceptual question. Insisting on exactly this interpretation against the word of the OP means calling him dishonest too. $\endgroup$
    – Dilaton
    Feb 23, 2014 at 18:11
  • $\begingroup$ @Dilaton no, you're focusing on the meaning of the words, whereas I'm talking about the phrasing. In a non-homework question, most people would write it as "Can this be answered without assumptions on the initial state?" or similar. $\endgroup$
    – David Z
    Feb 23, 2014 at 18:51
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    $\begingroup$ yes, IMHO focusing on the (physical) meaning of the words is a better way to look at things when judging question than exclusively concentrating on language or phrasing issues. Language issues are not the things that determine the physics merits of a question (think about non native English speakers too) and they can easily be fixed. Conversely, if the physics content of a question is not sufficient, this is much worse. BTW I just noted afterwards that my interpretation of the question is almost exactly what the OP wanted to express ;-) $\endgroup$
    – Dilaton
    Feb 23, 2014 at 19:18
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    $\begingroup$ No, phrasing is important too. There are certain phrasing styles characteristic of certain contexts - e.g. homework problems are written a certain way, conceptual questions are written a different way, non-native speakers have their own particular styles, and so on. $\endgroup$
    – David Z
    Feb 23, 2014 at 19:53
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    $\begingroup$ IMHO, while of course it is sometimes possible to deduce the origin of a text from its phrasing, in this case it never constituted very strong evidence. One might write "can you answer this without assumptions on the initial state?" just to be informal. Or one might write it if one had hung out a lot on math.SE, where questions are often phrased that way even if they're not copy-and-pasted. Such phrasing might be indicative of foul play, but it's not enough evidence in this case for the question to have been closed, IMO. $\endgroup$
    – N. Virgo
    Feb 24, 2014 at 0:52
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    $\begingroup$ I agree with @Nathaniel closing good legitimat interesting from a physics point of view questions for language reasons on a physics site, intended to do physics and not linguistics is quite far off the mark and inapproptiate IMHO. Leaving a comment that the language/phrasing should be improved, clarified is the far better way to go if needed. $\endgroup$
    – Dilaton
    Feb 24, 2014 at 11:21

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